What will the rivers of the Pacific Northwest look like in the future? Will they be stable or unstable? Will they have salmon or other species? Will the waters be cold and clear or warm and muddy? These questions motivate our study of the effects of climate warming on streams draining the Cascade Mountains.
Previous studies have shown that snowpacks throughout the Cascades are highly vulnerable to warming temperatures, readily changing from snow to rain, and melting earlier. Less certain is how these changes are likely to affect streamflows, particularly in streams that derive much of their flow from deep groundwater and springs. These groundwater streams, which are currently characterized by very stable bed, banks, and vegetation, are particularly sensitive to increasing peak flows in the winter. We want to know how changing snowpacks and increased peak flows are likely to affect these channels, potentially changing their suitability as habitat for threatened species such as bull trout and spring Chinook. Results from our work, which include field and modeling components, will be used to guide management decisions affecting these streams: how dams are operated, whether water suppliers need to worry about turbidity, and how we should manage riparian vegetation.
A key challenge for resource and land managers is predicting the consequences of climate warming on streamflow and water resources. Over the last century in the western US, significant reductions in snowpack and earlier snowmelt have led to an increase in the fraction of annual streamflow during winter, and a decline in the summer. This study explores the relative roles of snowpack accumulation and melt, and landscape characteristics or 'drainage efficiency', in influencing streamflow. An analysis of streamflow during 1950-2010 for 81 watersheds across the western US indicates that summer streamflows in watersheds that drain slowly from deep groundwater and receive precipitation as snow are most sensitive to climate warming. During the spring, however, watersheds that drain rapidly and receive precipitation as snow are most sensitive to climate warming. Our results indicate that not all trends in the western US are associated with changes in snowpack dynamics; we observe declining streamflow in late fall and winter in rain-dominated watersheds as well. These empirical findings have implications for how streamflow sensitivity to warming is interpreted across broad regions.
Changes in timing and magnitudes of streamflows under climate change pose significant risks to ecosystems, infrastructure, and overall availability of water for human use. We have developed a spatial analysis that predicts how both peak (winter) and low (summer) streamflows are likely to change in the future for Oregon and Washington. This set of spatial tools gives land managers a full toolbox with which to anticipate and plan for streamflow changes on forest lands.
Water stress represents a common mechanism for many of the primary disturbances affecting forests, and forest management needs to explicitly address the very large physiological demands that vegetation has for water. This study demonstrates how state-of-science ecohydrologic models can be used to explore how different management strategies might improve forest health.
Widespread threats to forests due to drought stress prompt re-thinking of priorities for water management on forest lands. In contrast to the widely held view that forest management should emphasize providing water for downstream uses, we argue that maintaining forest health in the face of environmental change may require focusing on the forests themselves and strategies to reduce their vulnerability to increasing water stress in the context of a changing climate. Management strategies would need to be tailored to specific landscapes but could include: a) thinning; 2) encouraging drought-tolerant species; 3) irrigation; and 4) strategies that make more water available to plants for transpiration. Hydrologic modeling reveals that specific management actions could reduce tree mortality due to drought stress. Adopting water conservation for vegetation as a priority for managing water on forest lands would represent a fundamental change in perspective and potentially involve tradeoffs with other downstream uses of water.
Bureau of Land Management, Oregon State University
Todd M. Wilson
Natural areas are special areas set aside for research, conservation, and education. There are over 580 natural areas in Oregon and Washington totaling >1.4 million acres and managed by 20 agencies and organizations. These include Forest Service Research Natural Areas (RNAs) as well as BLM RNAs and Areas of Critical Ecological Concern. Natural areas may one of the best network of sites for studying long-term effects of climate change and this project focuses on three areas of study. The first is to determine if natural areas adequately represent the depth and breadth of the natural ecosystems found in both states. The second is to prioritize sites that may be most vulnerable to climate change effects in the next several decades. Initial findings suggest natural areas are representative across several ecological gradients important for understanding effects of long-term climate and ecological change. In addition, several lists are being developed to help prioritize monitoring based on predictions from a broad range of existing climate change models. The third area of focus is to develop a standardized set of monitoring protocols for long-term monitoring of change using existing and new protocols. New methods being tested include use of terrestrial LIDAR plots to monitor changes in forest structure over time.
See more below
Massie, M. H. 2014. Assessment of the Vulnerability of Oregon and Washington’s Natural Areas to Climate Change. Master's thesis. Oregon State University, Corvallis, OR 97331.
The Forest Planner enables landowners in Oregon and Washington to find, map, and design custom forest management scenarios for their properties. Users can select the property and forest stands that they want to examine, enter information about the tree species and forest types represented, and select from a variety of management scenarios.
The Forest Planner enables landowners to visualize alternative forest management scenarios for their properties and their effect on variables including timber stocking and yields, carbon storage, and fire and pest hazard ratings.
Oregon State University, Wallowa-Whitman & Umatilla National Forests
This project will use climate-connected state and transition models developed as a part of the Integrated Landscape Assessment Project to assist with cumulative effects analysis of alternative management scenarios for the Lower Joseph project area in the Blue Mountains of Northeast Oregon. The objective is to use the climate-connected state and transition models to evaluate alternative scenarios proposed by local land managers and collaborative groups given possible climate change impacts.
This project will connect state and transition models developed as a part of the Integrated Landscape Assessment Project with Dynamic Global Vegetation Model outputs for Southeastern Oregon. The objective is to develop a set of vegetation modeling tools that can be used by local land managers and collaborative groups to examine potential rangeland management scenarios and interactions with possible climate change impacts.
This project will connect state and transition models developed as a part of the Integrated Landscape Assessment Project with Dynamic Global Vegetation Model outputs for Southwestern Oregon. The objective is to develop a set of vegetation modeling tools that can be used by local land managers and collaborative groups to examine potential forest management scenarios and interactions with possible climate change impacts.